1. Field of Invention
The present invention relates to methods of forming and detecting non-visible marks and articles marked in accordance with the methods.
2. Description of Related Art
Counterfeit goods are often manufactured, distributed, and sold in direct competition with authentic goods. The automotive parts market, for example, is flooded with counterfeit parts that outwardly appear to be authentic, but are not. Counterfeit parts are often not manufactured to the same tolerances and specifications as authentic parts, which can lead to safety and performance concerns. Some counterfeit automotive parts can so closely resemble authentic parts that it is nearly impossible for consumers to ascertain whether the parts are authentic or not.
Various authentication and/or anti-counterfeiting measures have been devised to attempt to combat the counterfeiting problem. For example, printed security labels are sometimes attached to authentic goods. Unfortunately, counterfeiters simply duplicate the printed security labels, including printed security labels that contain elaborate or complex anti-counterfeiting measures such as holographic images. Another problem with printed security labels is that the organic colorants, paper supports and adhesives generally cannot withstand exposure to high temperatures and harsh environmental conditions.
Non-visual markings have also been used to try to differentiate authentic goods from counterfeit goods. For example, some manufacturers apply ultraviolet (UV) fluorescent markings to authentic goods and documents. The markings are generally not visible until exposed to UV radiation whereupon they fluoresce and form a pattern or code that is intended to differentiate authentic goods from counterfeit goods. Unfortunately, conventional UV fluorescent markings and other markings that are contrastable outside of the visible portion of the electromagnetic spectrum are usually formed of organic pigments that can be readily duplicated. In addition, organic pigments are generally not able to withstand exposure to high temperatures and harsh environmental conditions, which makes them impractical for use in some applications such as the authentication of automobile parts.